1,721,028 research outputs found
The role of the peripheral target in stimulating eye movements
Full text linkThe present study investigated the role of top-down and bottom-up processes during a deceptive sports strategy called “no-look passes” and how microsaccades and small saccades modulate these processes. The first experiment examined the role of expertise in modulating the shift of covert attention with the bottom-up procedure. Results showed more saccades of greater amplitude and faster peak velocity in amateur than in expert groups. In the second experiment, the shift of covert attention between top-down and bottom-up conditions was investigated in a group of expert basketball players. Analysis showed that athletes make more microsaccades during the bottom-up condition; meanwhile, during the top-down condition, they were pushed to make more small saccades to decide where to send the ball. The findings suggested that the top-down process stimulates the eyes to move more concerning the bottom-up condition. It could be explained by the fact that during the top-down condition, athletes do not have an "eyehold” that stimulates their attention. During the top-down condition, athletes had to shift their attention to both sides before making the pass, resulting in their eyes being more "hesitant" concerning the situation in which they are peripherally stimulated
Driver’s Stress Detection using Skin Potential Response Signals
Full text linkStress in car drivers represents a risk, especially for professional car drivers
which are more likely to be exposed to it for prolonged periods. A persisting
stress state leads to mental and physical pathologies and increases the probability
of causing accidents. Thus, the monitoring of drivers’ mental state
could allow an immediate action before the problem degenerates.
In the present work, two main methods to detect a subject’s sympathetic reaction
to stress are developed. Method 1: we measure Skin Potential Response
(SPR) and record the Steering Wheel angle excursion. Then, we process the
measured signals with adaptive filters which remove the component related
to Motion Artifact, exploiting the relation between hand movements to handle
the Steering Wheel and MA. Next, we process the obtained Stress signal
with a Smooth Nonlinear Energy Operator (SNEO) to locate stress events.
Experiments which allow to define a ground-truth for stress events recognition,
show that, by appropriately processing, it is possible to efficiently detect
stress events, obtaining a mean Recall of 95 %.
Method 2: A double channel SPR sensor is used to measure SPR from both
the hands, and Electrocardiogram is recorded with a triple channel ECG sensor.
SPR measurements are processed through an algorithm which selects the
smoother signal. In this way we obtain a Stress signal without the Motion Artifact
component. Several experiments carried out in laboratory and with a
real car professional simulators, reveal the efficacy of the proposed system,
which outperformed Principal Component Analysis and Independent Component
Analysis.
Next, machine learning techniques are employed to classify features obtained
from the Stress signal and from Heart Rate Variability. In particular, we considered
a Support Vector Machine (SVM) and a feed-forward Neural Network
(NN). The system is tested in experiments carried out on a professional
driving simulator. Classifying 15 seconds long time intervals, we obtained a
balanced accuracy of 76.72% for SVM and 77.15% for NN. Applying a relabeling
method based on the previous time intervals, the performances raised
to 78.74% for SVM and 78.26% for NN. We then, tested the ability to identify
stress intervals and obtained a balanced accuracy of 89.58% for SVM and
91.92% for NN
Acute Cardiovascular and Metabolic Effects of Different Warm-Up Protocols on Dynamic Apnea
Full text linkThe aim of this study was to evaluate the acute physiological response to different warm-up protocols on the dynamic apnea performance. The traditional approach, including a series of short-mid dives in water (WET warm-up), was compared to a more recent strategy, consisting in exercises performed outside the water (DRY warm-up). Nine athletes were tested in two different sessions, in which the only difference was the warm-up executed before 75m of dynamic apnea. Heart rate variability, baroreflex sensitivity, hemoglobin, blood lactate and the rate of perceived exertion were recorded and analyzed. With respect to WET condition, DRY showed lower lactate level before the dive (1.93 vs. 2.60 mmol/L, p = 0.006), higher autonomic indices and lower heart rate during the subsequent dynamic apnea. A significant correlation between lactate produced during WET with the duration of the subsequent dynamic apnea, suggests that higher lactate levels could affect the dive performance (72 vs. 70 sec, p = 0.028). The hemoglobin concentration and the rate of perceived exertion did not show significant differences between conditions. The present findings partially support the claims of freediving athletes who adopt the DRY warm-up, since it induces a more pronounced diving response, avoiding higher lactate levels and reducing the dive time of a dynamic apnea
Modeling the dynamic processing of the presynaptic terminals for intrabody nanonetworks
No full textExperimental evidences show that: 1) the release sites from a single axon have variable release probabilities, even when the axon contacts the same postsynaptic neuron; 2) this variability in the release probability implies a compartmentalization at the level of the presynaptic terminals of the neuronal processing; 3) the specificity of the presynaptic terminal processing is driven by and reflects the complex biophysical mechanisms activated at the axon terminals when a spike is fired in response to a stimulus. Stemming from these experimental evidences, we propose a communication engineering model for capturing the behavior of biological neurons. Specifically, by adopting a stochastic approach, the presynaptic terminals are modeled as a dynamic array of transmitters, where each transmitter models the processing specificity of a presynaptic terminal. In particular, we first show that the unique and specific processing of a presynaptic terminal can be reconducted to the cascade of a frequency selector and an amplitude modulator. Then, we characterize the propagation of the presynaptic-filtered signal through the synaptic cleft, and we derive the delay along with the channel attenuation as a function of the distance between the communicating neurons. Finally, the theoretical analysis is validated through numerical simulation
Investigating the Crucial Role of Optic Flow in Postural Control: Central vs. Peripheral Visual Field
Full text linkOptic flow stimuli are crucial for the control of stance in the upright position. The visual control of posture has recently received a lot of interest from several researchers. One of the most intriguing aspects is the contribution of the different parts of the visual field in the control of stance. Here we reviewed the results of several studies performed with different methodologies that tried to determine the effect of optic flow on postural control, by analyzing the role of the central and peripheral visual fields. Although the results were controversial, the majority of these studies agreed to assign the most important role in postural control to the peripheral retina. However, these studies were performed using different approaches and different definitions of the central and peripheral visual fields. The choice of the exact portion of the retina to be stimulated is crucial given that the stimulation of the central and the peripheral parts of the retina leads to the activation of different geniculo-cortical pathways and results in different cortical processing of information
Evaluation of the Effectiveness of Compression Garments on Autonomic Nervous System Recovery After Exercise
Full text linkThe aim of this investigation was to evaluate the recovery pattern of a whole body compression garment on hemodynamic parameters and on ANS activity following a swimming performance. Ten young male athletes were recruited and tested in two different days, with and without wearing the garment during the recovery phase. After a warm-up of 15 minutes, athletes were instructed to perform a maximal 400m freestyle swimming event, and then time series of beat-to-beat intervals for heart rate variability (HRV), baroreflex sensitivity (BRS), and hemodynamic parameters were recorded for 90 minutes of recovery. The vagally mediated HF power of R-R intervals, NN50, and pNN50 showed a faster recovery due to the costume, meanwhile, the LFRR index of sympathetic modulation of the heart, as well as LF:HF ratio and BRS alpha index (αLF) were augmented in control than in garment condition. When athletes wore the swimsuit, cardiac output was increased and the returning of the blood to the heart, investigated as stroke volume, was kept constant due to the reduction of the total peripheral resistances. During control condition, HR was restored back to baseline value 20 minutes later with respect to garment condition, confirming that the swimsuit recover faster. The effectiveness of the swimsuit on ANS activity after a maximal aerobic performance has been shown with a greater recovery in terms of HRV and hemodynamic parameters. BRS was reduced in both conditions, maybe due to prolonged vasodilatation that may have also influenced the post-exercise hypotension
A Narrative Literature Review About the Role of Microsaccades in Sports
Full text linkIn many daily and sport situations, people have to simultaneously perceive and process multiple objects and scenes in a short amount of time. A wrong decision may lead to a disadvantage for a team or for a single athlete, and during daily life (i.e., driving, surgery), it could have more dangerous consequences. Considering the results of different studies, the ability to distribute visual attention depends on different levels of expertise and environment-related constraints. This article is a narrative review of the current scientific evidence in the field of eye movements in sports, focusing on the role of microsaccades in sporting task situations. Over the past 10 years, microsaccades have become one of the most increasing areas of research in visual and oculomotor studies and even in the area of sport science. Here, we review the latest findings and discuss the relationships between microsaccades and attention, perception, and action in sports
Convolutional Neural Networks Using Scalograms for Stress Recognition in Drivers
No full textIn this paper we present a system which allows the detection of stress in drivers by analyzing a two-dimensional representation of their electrodermal activity Skin Potential Response (SPR) signal, and their electrocardiogram signal. Signals were logged during a simulated drive, in an experiment carried out in a company using a professional car driving simulator. Subjects had to overcome some stress-inducing events located at specific positions during the drive. The acquired SPR and heart rate signals are analyzed with scalogram plots, in order to obtain a time-frequency representation of the signals. The 2D scalogram representation is segmented into images, associated to short time segments, which are classified using a Convolutional Neural Network architecture. We show that the use of scalograms can allow the system to perform well in distinguishing among stress and non-stress situations, achieving a 91.78% accuracy. The same system was tested on real driving data available from a public dataset, achieving a 99.24% accuracy
A comparison of perceptual anticipation in combat sports between experts and non-experts: A systematic review and meta-analysis
Full text linkIn order to systematically evaluate perceptual anticipation between experts and non-experts for different kinds of combat sports, we needed to perform a comprehensive assessment. In this systematic review and meta-analysis, we searched four English-language and three Chinese-language databases that used expert/non-expert research paradigms, to explore perceptual anticipation in combat sports. We employed a random effects model for pooled analyses using the inverse variance method. We included 27 eligible studies involving 233 datasets in this meta-analysis. We observed large effect sizes for the differences between experts and non-experts in both response accuracy (1.51; 95% CI: 1.15 to 1.87, p < 0.05) and reaction time (-0.91; 95% CI: −1.08 to−0.73, p < 0.05). We also observed substantial differences between experts and non-experts in the mean duration of visual fixations per trial (1.51; 95% CI: −2.40 to −0.63, p < 0.05), but not in the visual fixation duration (0.16; −061 to 0.92, p = 0.69). Taken together, high-level combat athletes have more advantages in perceptual anticipation than lower-level athletes, showing faster and more accurate responses when facing the opponent's attacks, as well as focusing on fewer points of visual fixations than novice athletes. Different types of combat sports and stimulus presentations affect perceptual anticipation abilities to varying extents in relation to outcome measures, with more pronounced expertise in a stimulus that is closer to real-world situations. SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021226343, PROSPERO CRD42021226343
Effect of heading perception on microsaccade dynamics
No full textThe present study shows the relationship between microsaccades and heading perception. Recent research demonstrates that microsaccades during fixation are necessary to overcome loss of vision due to continuous stimulation of the retinal receptors, even at the potential cost of a decrease in visual acuity. The goal of oculomotor fixational mechanisms might be not retinal stabilization, but controlled image motion adjusted to be optimal for visual processing. Thus, patterns of microsaccades may be exploited to help to understand the oculomotor system, aspects of visual perception, and the dynamics of visual attention. We presented an expansion optic flow in which the dot speed simulated a heading directed to the left or to the right of the subject, who had to signal the perceived heading by making a saccade toward the perceived direction. We recorded microsaccades during the optic flow stimulation to investigate their characteristics before and after the response. The time spent on heading perception was similar between right and left direction, and response latency was shorter during correct than incorrect responses. Furthermore, we observed that correct heading perception is associated with longer, larger and faster microsaccade characteristics. The time-course of microsaccade rate shows a modulation across the perception process similar to that seen for other local perception tasks, while the main direction is oriented toward the opposite side with respect to the perceived heading. Microsaccades enhance visual perception and, therefore, represent a fundamental motor process, with a specific effect for the build-up of global visual perception of space
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